This freezes the slots on a DC client so no one else can connect (because all slots are full). Plain and simple, this is a pure leech mentality.

This is simply caught for DC clients because it ALWAYS will allow a filelist upload (well, most often; I won't go into details), regardless if slots are full. There is a version of DC out there that will allow only OPs to get the users filelist and lock the slots for normal users.